To explore the microscopic world, people have been using conventional optical microscopy for a long time. However, due to the diffraction limit the highest resolution of conventional optical microscope is only about λ/2, where λ is the wavelength of illuminating light. As a result, the conventional optical microscope could not be used to see objects smaller than ˜200 nm when using visible light. To break the diffraction limit, one current approach is based on Near-field Scanning Optical Microscope (NSOM) [1], which has found wide applications in nano-technologies, materials science, biology and other areas. The advantages of NSOM imaging include: sub-wavelength resolution (50-200 nm) using visible or near-IR light, simultaneous acquisition of optical and topographical information, capable of imaging aqueous samples. In addition, since NSOM imaging system is able to use various light sources to illuminate specimen surface, it may provide more functions, such as excitation and fluorescence of material under study.
However, one main limitation of NSOM is the very low light power throughput of its near-field scanning tip, typically 10−3 to 10−6 throughput for 200 nm to 50 nm wide tip apertures [2] at λ=500 nm. Another limitation of NSOM is that it requires the mechanical scanning of the near-field tip to image an object, which will inevitably lead to a slow-speed and still-object only imaging.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.